Rotary stirling cycle engines



Feb. 27, 1968 D. A. KELLY 3,370,418

ROTARY STIRLING CYCLE ENGINES Filed Oct. 24, 1966 2 Sheets-Sheet 1 I g- I Z W; W Z6 77 U [A 22 74 \\\\\w INVENTOJZ,

Feb. 27, 1968 D. A. KELLY 3,370,418

ROTARY STIRLING CYCLE ENGINES INVENTOR:

United States Patent ()fifice 3,370,418 Patented Feb. 27, 1968 3,370,418 ROTARY STIRLING CYCLE ENGINES Donald A. Kelly, 58-06 69th Place, Maspeth, NY. 11373 Filed Oct. 24, 1966, Ser. No. 588,799 7 Claims. or. 6024) This invention relates to a new pressurized rotary Stirling cycle engine, including both axial and radial gas flow types.

Various types of pressurized reciprocating Stirling engines are well known in the field and while most are efficient, 'all are hampered by the requirements of connecting rods and the sealing of these rods in addition to linkage and the wear inherent in these connections.

The rotary type of engine is designed to achieve the efliciency and silence of the Stirling cycle in a simpler, easily produced engine arrangement, while gaining the inherent benefits of a rotary machine.

The classic Stirling closed cycle is basically an externally heated engine in which the constant volume of gas is alternately heated and cooled to produce the half power stroke and half pull stroke, on the power piston. The conventional reciprocating Stirling engine currently in use consists of dual coaxial pistons, one displacer and one power piston reciprocating within a common cylinder. The approximate 90 degree phase angle at the crankdisc keys the cycle so that the displacer piston follows the power piston downward for the half power stroke, thereby allowing the expanding gases to push effectively on the power piston. The two pistons are in-line and connected in phase to a common crankdisc and shaft. In a similar manner the displacer piston follows the power piston on the upward half pull stroke.

Since the conventional Stirling engine combines the cold clearance volume with the power piston volume, a certain amount of thermal loss occurs when the hot expanding gases contact the cold wall areas, with a corresponding loss of efiiciency.

A further unavoidable deficiency in the common cylinder diameter design is that the compression ratio is inherently set at a low value of about 2.5 to 1.

This low compression ratio leads to the application of undesirably high internal pressure in order to produce competitive power-to-displacement ratios of approximately 2 horsepower per cu. in.

In the rotary design a rotary displacer takes the place of the displacer piston and the power rotor and vanes take the place of the power piston. In the axial flow or tandem arrangement the alternately expanding and contracting gas is impelled by the flow blades to enter and leave the respective ports of the power section.

These ports are staggered radially to match the pitch direction of the flow blades which produce a zone and torroidal flow effect within the displacer cylinder. This is not an ideal system since the cold zone is compromised, by being the inner zone, in favor of the hot outer zone expansion efiiciency.

The hot expanding gases enter the hot port and expand against the power rotor and vanes to cause rotation during the hot expansion phase of approximately onehalf rotation. The cooled gas contracts to cause a partial vacuum within the displacer cylinder and thereby cause evacuation within the varying chamber of the power section. This evacuation causes a pull on the rotor vane, for approximately one-half rotation.

The alternate heating and cooling of the gas caused by the rotary displacer fiat nearly duplicates the action of the displacer piston in a reciprocating engine and the rotation of the power rotor assembly nearly duplicates the resultant motion of the power piston of the reciprocating engine.

In the radial fiow or parallel cylinder arrangement th hot expanding gases are forced centritugally, by the r0- tation of the rotor flat, into the hot duct and into the power section where they act on and rotate the power rotor and vanes. During the cold half-cycle the contracting gases cause a vacuuming effect in the cold duct and thereby create a pull on the power rotor assembly.

This system is somewhat more efficient than the axial flow arrangement, since there is no intermingling of thermal zones within the displacer cylinder, due to the separation of the hot and cold ports across the diameter of the cylinder.

The same displacer rotor and flat arrangement are utilized in this radial flow type of engine. The two cylinders, displacer and power are connected together with a chain drive or equivalent drive. The drive ratio will be approximately one-to-one. The relative volumes of the two section cylinders should be at a ratio of about tento-one, displacer-to-power, in order to operate properly.

The problem of thermal regeneration in the rotary engine is diificult and at best not as efiicient as would be desired.

Since external regeneration is complex, circular regenerator bores within the displacer rotor seem the most reasonable and feasible to construct. These multiple circular bores would be filled with a regenerative filament for thermal storage. In operation the filament would store heat during the rotor passage through the hot side of the displacer cylinder, retain it, and expel it when the rotor flat reenters the hot side of the cylinder.

It is an object of the invention to create a simpler Stirling cycle engine while maintaining all the superior characteristics of the cycle.

It is an object of the invention to create an improved Stirling cycle engine by utilizing the advantages of pure rotational elements.

It is an object of the invention to achieve maximum operating efliciency in a rotary engine by the adoption of new regeneration and thermal saturation techniques.

It is an object of the invention to produce long-lived, trouble free, and relatively inexpensive rotational seals and elements.

It is an object, in view of the aforementioned objects, to produce a rotary Stirling engine that is relatively inexpensive and easy to manufacture.

Other features and objects will become apparent from the following description of the engine design.

It should be understood that variations may be made in the detail design without departing from the spirit and scope of the invention.

Referring to the drawings:

FIG. 1 is a front section through the displacer cylinder.

FIG. 2 is a side section through the engine.

FIG. 3 is a front section of an alternate two parallel cylinder arrangement.

FIG. 4 is a side view of the first power vane.

FIG. 5 is an end view of a power vane.

FIG. 6 is a side view of the second power vane.

Referring to the drawings in detail: the cylindrical displacer housing 1 is fitted with the front plate 2 and the rear plate 3. The screws 27 hold both plates in place on the displacer housing. The displacer rotor 4 closely fits and revolves in the displacer housing 1 and rotates with the main shaft 5. The two rotor bearings 6 support displacer rotor and main shaft within the displacer housing. The front flange 7 carries the shaft seal 8, which pressure seals the main shaft 5 in the housing. The front flange 7 is secured to the front plate 2, by the screws 26. Liquid sealant is usedto make a pressure tight seal between the front flange and the front plate 2.

The displacer rotor 4 has a flat 21 that is approximately located at one-quarter the radius of the displacer rotor from its outside diameter. This fiat forms the basic gas working volume of the engine. Multiple guide rings 22 support the flow blades 23, 24, 25, and are secured to the rotor flat. The flow blades 24 are the symmetrical center blades which match the number of guide rings and are secured to them. The side blades 23 and 25 are of opposite hand to each other and are secured to the guide rings 22, as indicated.

The displacer rotor is built up to be solid and pressure tight and may have internal counterbalancing to simplify the final dynamic balancing of the rotor assembly.

The power cylinder 9 is secured to the end plate 10 and 11 by the screws 28 and 29. The screws 29 also secure the end plate 10 to the rear plate 3, which serve to tie the two engine sections together. The gasket 20 seals both end plates to the power cylinder.

The slotted power rotor 12, is supported by the main shaft and bearing 19, and eccentrically fits and revolves in the power cylinder9. The main shaft protrudes into the power rotor about one-third the rotors full width in order to provide working space for the two power vanes.

'The power rotor is held in place on the main shaft by the key 18.

i The power rotor vanes 13 and 14 fit into their respective slots of the power rotor at right angles to each other. Due to their shape they interfit and have independent radial motion within their own slots. 7

The seals 15 and 16 and their loading springs 38 fit into their respective slots of the rotor vanes 13 and 14. The loading springs provide a small preload to the rotor seals to assure adequate contact and pressure sealing at the inside walls of the power cylinder.

The top and side seals overlap each other by lap joints in order to provide continuity of sealing within the power cylinder. 7

The hot twin ports 31, and cold twin ports 30, allow thealternate hot and cold gas fiow from the displacer cylinder to enter and leave the power cylinder. These ports are lined up within the crescent-shaped cavity produced by the eccentricity of the power rotor Within the power cylinder, and the ports'sets, hot and cold are about 150 degrees apart.

The mating surfaces of the two engine cylinders is sealed by liquid sealant made pressure tight by tightening the connecting screws 2.

The inside surfaces of the power cylinder are lined I with a dry film lubricant such as moly-disulphide or similar lubricant for dry lubrication operation. If necessary an oil lubrication system may be provided to increase the life of the rotor vane seals which may be made of filled-Teflon or other equivalent seal material.

The displacer cylinder 1, must be fitted with a pressure filler receptacle 36, a pressure gauge 37, a pressure relief valve .34 and a temperature gauge 35.

Multiple regenerator bores 39 are located in the displacer rotor 4 which are filled with the regenerative filament 40. The bore openings start and end on the rotor fiat and the bores are concentric with the displacer rotor center. In operation, when the rotor revolves and the flat is at the hot side, some of the hot expanding gas enters the regenerator bores and is stored during the half revolution thru the cooled side. As the rotor flat just revolves into the hot side the stored hotigas is expelled into the hot volume to boost. and preheat the hot gas volume.

Conversely, part of the cooled, contracting gas enters the regenerator bores during the rotor half revolution thru the cold side and is stored during the half revolution precool the cooling gas volume.

The heat source44 is located at one side of the displacer cylinder and the cold source 45 is located at the opposite side of the displacer cylinder-480 degrees from the hot source. The heat source 44, would consist of a conventional fuel burner arrangement for the combustion of kerosene, fuel oil or other low grade liquid fuels.

The burner system must be draft and gust proof and provided with a pilot light system. The system must also be capable of operation at four or five different heat levels for engine power control.

. The cold source 45, must consist of cold water tubing which criss-cross the cylinder surface and are closely spaced and in direct contact with the surface. Other cooling means may be utilized providing they are equally as eificient as the liquid cooled system.

Thin metal strips 41, are secured to the inside diameter of the displacer cylinder, which flex partly into and out of the gas volumes. The strips are closely spaced and must clear the flow blades and rings.

v The purpose of the flex strips is to further conduct and more rapidly transfer heat and cold to the gas volume,

providing a heat in depth. The strips must not protrude too deeply into the rotor arc, since their fiexural displacement must be kept low for reasonable life.

The engine assembly is provided with a variable pres-.

sure system for speed/power control, since varying the pressure level quickly provides speed response.

In the radial flow,- parallel cylinder arrangement all of the basic elements and arrangement are the same as in the axial flow type except for the external connections and orientation.

The hot transfer duct-32 at the top connects the hot ports 31, in the displacer cylinder with the hot ports of the power cylinder.

The cold transfer duct 33. at the bottom connect vthe cold ports 38, in the displacer cylinder with the cold ports of the power cylinder. 7

The only difference within'the displacer cylinder l is that all the flow blades, 23, 24, 25 have no pitch so that the gas flow is directed radially into the hot and cold ports in the circumference of the displacer cylinder.

It should be observed that there is a similarity in the rotary Stirlin cycle engine to that of the closed cycle gas turbine in that the displacer rotor functions as the compresser stage and the power rotor functions as the turbine, power stage. The basic difference is in the operating medium and alternate hot and cold cycling,

What is claimed is:

1. A dense gas rotary Stirling cycle engine comprising a first cylinder, a truncated rotor within said cylinder, multiple rings mounted on said truncation, multiple impeller blades mounted on said rings, a shaft to support said truncated rotor, two end plates to enclose said first cylinder, multiple ports within one of said end plates, and bearings within said end plates to support said shaft,

a second cylinder in line with said first cylinder, a slotted rotor within said second cylinder havinga short blind hole for said shaft, two movable vanes at right angles within said rotor, sealing means in said movable vanes, two end plates to enclose said se 7 0nd cylinder, multiple ports within one of said end plates which freely communicate with the multiple ports within one of the said end plates of said first cylinder, bearing means for said first and second cylinders, means for sealing said shaft where it pro,- jects from the said first cyl nder.

.2. A dense gas rotary Stirling cycle engine, according toclairn 1, in which said truncated rotor contains multiple circular regenerator bores filled with fine filament, internal countcrbalancing means.

3. A dense gas rotary Stirling cycle engine, according to claim 1, in which the said truncated rotor is of thru the hot side. It is expelled into'the cold volume to irregular shape, shaped.

4. A dense gas rotary Stiriing cycle engine comprising a first cylinder, a truncated rotor within said first cylinder, multiple rings mounted on said truncation, multiple impeller blades mounted on said rings, a shaft support said truncation is wave or helically said truncated rotor, two end plates to enclose said first cylinder, multiple ports within the walls of said first cylinder, and bearings Within said end plates to support said shaft,

a second cylinder located parallel with said first cylinder, a slotted rotor within said second cylinder having a short blind hole for said shaft, two movable vanes at right angles within said rotor, sealing means in said movable vanes, two end plates to enclose said second cylinder, multiple ports within the walls of said second cylinder which freely communicate with the multiple ports within the walls of said first cylinder, sealing means for said first and second cylinder, means for sealing said shaft where it projects from said first cylinder,

an exterior duct connecting said first cylinder ports with the second cylinder ports at the top of each, an exterior duct connecting said first cylinder ports at the bottom and disposed diagonally upward and connecting to said second cylinder ports,

external connecting and drive means from said first cylinder shaft to a second shaft within said second cylinder.

5. A dense gas rotary Stirling cycle engine according to claim 4 in which said movable vanes are increased in number and are independently spring controlled.

6. A dense gas rotary Stirling cycle engine, according to claim 4 in which the said first cylinder is fitted with a plurality of thin flexible metal strips on the inside walls, external regeneration ducts are placed around the said first cylinder between the hot and cold areas, heating and cooling means for said first cylinder.

7. A dense gas rotary Stirling cycle engine according to claim 4, in which the said first and second cylinders are in line, an exterior duct connecting said first cylinder top ports with the said second cylinder top ports, an exterior duct connecting said first cylinder bottom ports with the said second cylinder bottom ports.

No references cited.

WENDELL E. BURNS, Primary Examiner. 

1. A DENSE GAS ROTARY STIRLING CYCLE ENGINE COMPRISING A FIRST CYLINDER, A TRUNCATED ROTOR WITHIN SAID CYLINDER, MULTIPLE RINGS MOUNTED ON SAID TRUNCATION, MULTIPLE IMPELLER BLADES MOUNTED ON SAID RINGS, A SHAFT TO SUPPORT SAID TRUNCATED ROTOR, TWO END PLATES TO ENCLOSED SAID FIRST CYLINDER, MULTIPLE PORTS WITHIN ONE OF SAID END PLATES, AND BEARINGS WITHIN SAID END PLATES TO SUPPORT SAID SHAFT, 